The present invention is directed to an apparatus and method for printing a graphic onto a continuously moving sheet of work material, and will be described herein as applied to such use.
In known printers, a single print head is usually mounted on a frame for movement transversely across a piece of sheet-type work material. In many instances the print head includes a print cartridge having an ink reservoir and a number of discrete inkjets arranged in a matrix-like pattern adjacent to the media to be printed. This matrix-like pattern of inkjets is referred to by those skilled in the pertinent art as an array.
Typically, a line of a graphic is printed onto the work material by causing the print head to traverse the work material while the work material is stationary. As the print head moves, the inkjets spray appropriately colored ink onto the work material in accordance with commands issued from a controller. The work material is then incrementally advanced an amount preferably equal to the height of the array of inkjets, and the print head makes another pass across the work material. This process of incrementally advancing the work material and printing, is continued until the entire graphic is printed onto the work material.
A problem associated with printing a graphic in this manner is that due to the incremental indexing and stopping of the sheet material advancement, the process of printing a large graphic becomes very time consuming, and expensive. In addition, in large printing applications, it is often necessary to accelerate and decelerate large rollers of sheet material.
Moreover, the discrete motion of the sheet material as it is advanced can cause slight misalignments, that in turn generate inaccuracies in the printed graphic. In addition, after a line is printed the work material must be advanced an amount equivalent to the height of the array of inkjets defined by the print cartridge. Any deviation will either cause overlap or gaps between successive printed lines depending on whether the work material advanced too far or too little.
Based on the foregoing, it is the general object of the present invention to provide a plotter that overcomes the above-described problems and drawbacks present in the prior art.
It is a more specific object of the present invention to provide a printer that can print a graphic onto a piece of sheet-type work material that is continuously fed through the printer without having to stop the advancement of the work material.